Filamentary product and method of its production



H. E. HOLCOMB 7 April 25, 1950 FILAMENTARY PRODUCT AND METHOD OF ITSPRODUCTION 2 Sheets-Sheet 1 Filed July 27, 1948 lNVENT OR flaw/Pr5156460415. 4/{7Li0 TTORNEY April 25, 1950 H. E. HOLCOMB FILAMENTARYPRODUCT AND METHOD OF ITS PRODUCTION 2 Sheets-Sheet 2 Filed July 27,1948 Patented Apr. 25, 1950 umrsu STATES PATENT orncs FILAMENTARYPRODUCT AND METHOD OF ITS PRODUCTION Harry E. Holcomb, Stratford, Com,

Johns-Manville Corporation, New York, N.

assignor to Yo,

a corporation of New York Application July 27, 1948, Serial No. 40,81616 Claims. (Cl. 154-124) 2 with the filaments of each layersubstantially parallel and the filaments of adjacent layers crossing atacute angles, is drawn or expanded by pulling the mat in a. directionsubstantially provision of an improved product of this type of lesserdensity and more open texture adjacent one surface than the other, thetexture and density preferably gradually changing through at rightangles to the general lay of the filaments. the operation beingcontinued until layers of the mat corrugate and the mat as a whole puflsup or expands in the direction of its thickness. In accordance with theinstant invention, expansion of the mat is retarded adjacent one surfaceand is accelerated adjacent .the other, whereby the mat puffs to alesser extent and, hence, is denser adjacent one surface than the other,the

' intermediate structure of the body varying bethe thickness of theproduct from the one condition to the other. The product suitablycontains a minor proportion of a binder which re-. tains the filamentsthereof in their positions and bonds the whole into a unitary body. Theproduct is of particular utility as an air filter medium. Thesurface ofless density and more open texture is employed as the air entry side ofthe filter and, as the'dust-laden air enters the body, the coarse dust,lint and the like are removed. As the air passes on through the body thefiner dust is progressively deposited, the relatively dense structureadjacent the opposite surface forming a final clean-up section to removeany remainder of the dust. The single unit is thus comparable to aseries of filters of varying dustremoval characteristics. By removingthe coarse dust and lint in the more open section, it is possible toobtain a greatly increased dust retention capacity before resistance toair flow becomes excessive. It will be appreciated, however, that theproduct may find other fields of usefulness than.

air filters.

Another object of the invention is the provision of a multi-layer, glassfilament mat pulled or expanded in the direction of its thicknesscomprising a plurality of layers having substantially parallelcorrugations or undulations, the undutween the two extremes. contains abinder which is applied in an unset state to the original mat to insuredistribution throughout the mat and is set after the expansionoperation. Where a product of higher density is desired, the puffed bodyis compressed and held in that condition during the binder settingoperation.

My invention will be more fully understood and further objects andadvantages thereof will become apparent when reference is made to themore deta led description of the preferred embodiment of the inventionwhich is to follow, and to the accompanying drawings in which:

Fig. 1 is a perspective view of a segment of an expanded product inaccordance with the instant invention;

Fig. 2 is a view similar to Fig. 1 illustrating a modified embodiment;

Fig. 3 is a diagrammatic, end elevational view of an apparatus employedin preparing the initial mat from which the instant structure isderived;

Fig. 4 is a diagrammatic, front elevational view of the apparatus ofFig. 3;

Fig. 5 is a plan view of the mat as made on the apparatus of Figs. 3 and4;

Fig. 6' is a diagrammatic, elevational View of the apparatus embodyingthe instant invenion;

Fig. 7 is a top plan view of the apparatus of,

i Fig. 6; and,

Fig. 8 illustrates a modified construction of a portion of theapparatus.

Referring now to the drawings, a product of the instant inventionconsists of a body in composed of a plurality of layers l2, each formedof continuous, or substantially continuous glass filaments It. Thefilaments of each layer lie in approximate parallelism and the filamentsof adjacent layers cross each other. The product is pulled or expandedin the direction of its thick- Suitabiy the product ness to produce alightweight, low density material. In the expanding and pullingoperation in accordance with the instant invention, the filamentarylayers, particularly those adjacent one surface of the product, theupper surface of Fig. l, are corrugated and the corrugations are broughtinto relatively adjacent, lateral relationship. At the same time thecorrugated layers are somewhat separated, although tied together by a.multiplicity of interconnecting filaments, to form a very low density,open work structure. The corrugations or undulations of the layersinwardly of the surface are gradually of lesser depth as the oppositesurface is approached, the layers adjacent the opposite surface beingonly slightly corrugated or at least having corrugations of relativelyshallow depth as compared with the layers adjacent the other surface.The separation between the layers also progressively decreases as theopposite surface is approached and the density of the productproportionately increases.

Intermingled with the filaments of the several layers, and bonding themass of fibers into a unitary body, is a minor proportion of a binder,say between and by weight of the product. It will be understood thatFig. 1 is diagrammatic and that in actual practice the binder particlesillustrated by reference character l6 will be visually insignificant.

The product shown in Fig. 2 is of the same character as that shown inFig. 1 except in thb case the body has been compressed from thethickness shown in Fig. 1 and maintained in compressed state by the setbinder. In this embodiment similar gradation of structure of the body ispresent but the body is proportionately denser throughout.

The products described above are adapted for many uses but areparticularly valuable as air filtering media as previously explained.The products are very lightweight and a great multiplicity of fine,intercrossing filaments form a reticulated structure well adapted toremove particulate matter from air or other gases. The gradual increaseof density and decrease of the size of the interstices permits agraduated removal of the dust particles, the larger particles beingcaught or held adjacent the more open side of the filter body. Thegreatest mass of the particles E removed from the airstream by theintermediate layers and the residue of fine particles which penetratesubstantially through the body are collected by the final relativelydense layers. The body may be used in its compressed form, particularlywhere finer dust particies are present. and exceptional high efilciencyis required. In both forms a large filtering capacity is obtained due tothe distribution of the deposited dust throughout the body.

Referring now particularly to Figs. 38 inclusive, the method andapparatus employed to produce the products described above will beexplained in detail. The products are made from the initial mat l8 (seeFig. 5), known as the condensed mat, fabricated in a substantiallyconventional manner by drawing a plurality of continuous glass filamentsdirectly from the spinning orifices of the melting furnace 22 andaccumulating the filaments on a drum 24. The drawing drum is rotated inthe direction indicated by the arrow in Fig. 3 by any suitable drivingmeans (not shown) and at a relatively high speed to continuously drawfine filaments, say, of 6 to 30 micron diameter, and wind the filamentson the drum. Either the furnace or the drum is reciprocated to lay thefilaments on the drum in a plurality of layers of spirals with thefilaments of each layer crossing the filaments of adjacent layers. Inthe apparatus illustrated, the furnace 22 is reciprocated, as indicatedby the doubleended arrow in Fig. 4. The rate of reciprocation relativelyto the drawing speed, that is the peripheral speed of the drum, is suchthat the filaments of adjacent layers cross each other at acute angles.

A binder may be applied during the filament drawing operation. Thisapplication may be made in any suitable way, for example by a manuallyoperated spray device 26 (see Fig. 3), which is moved back and forthacross the mat on the drum at intervals to uniformly spray the bindermaterial onto the mat. The amount of binder used is carefullycontrolled. As will later be explained in greater detail, only a portionof the total binder content, say up to 70%, is preferably applied atthis stage, the remainder of the binder being applied to the mat duringlater stages in the formation of the product. The total binder used issuch that th solids binder content of the finished product is, say, 1 to5% by weight of the product.

The binder is preferably employed in the form of an emulsion, a waterdispersion being suitable. However, a solution of the binder in asolvent may also be employed. The binder may be either thermosetting orthermoplastic, but thermosetting adhesives are referred. Examples ofsuitable matezials are acrylic resins, urea-formaldehyde resins,polyvinyl alcohols, latices, and the like. In commercial operations ithas been found preferable to apply a water dispersion of an acrylicresin during the filament drawing operation and a dispersion of aurea-formaldehyde resin at the later stage. Due to the relatively highspeed movement of the mat on th drum and the temperatures prevalentduring the filament drawing operation, the binder rapidl dries byevaporation of the water or solvent, as the case may be, so that, uponcompletion of the drawing operation, the mat contains a substantiallydry but unset binder.

When the condensed mat is completed, it is severed along a line ofgeneration of the drum and is removed therefrom. The mat is then placedon a conveyor 28 of a feed device including a conveyor 30 mounted in asuitable manner to overlie the forward end of conveyor 28 and toyieldably engage the latter. While the condensed mat is on conveyor 28and before it is fed beneath the overlying conveyor, it is treated witha binder softener. In the case of a binder such as the preferred acrylicresin, the softener is water, which in eifect again places the finelydivided binder in suspension. If binders are employed of the type whichcannot be practically softened with water, an appropriate solvent isused. The softener may be applied to the mat in the form of a spray, ora hand brush, illustrated at 32, may b employed for the purpose. Aspointed out above, preferably although not necessarily, only a port-ionof the total binder content was applied to the condensed mat during thewinding operation. Where this practice was followed the remainder of thebinder is applied at this time. The added binder may be the same as thatalready used but suitably is a material such as a urea-formaldehyderesin. This material, in the form of a suspension, is spread on the maton the conveyor, simila:ly as the softener. When the mat has beentreated as described above, it is allowed to stand for an appreciablelength of time to-permit thorough soaking of the mat.

Referring now specifically to Figs. 6 and 7, the apparatus for expandingthe mat, prepared as explained above, will be described. This apparatus,in addition to feed conveyors 28 and 30, previously mentioned, includesin its preferred embodiment, a substantially level table or plate 34having a forwardly and downwardly angling side flange 36, a

lower roll 38 and an upper roll 40. Rolls 38 and 48 are supported to bedriven at regulated speeds by suitable-means (not shown). An oven 42 isprovided forwardly of the rolls, the oven including a conveyor 44supported at th rear end by pulleys 48 and 48 for movement in thedirection indicated by the arrow by any suitable drivin means (notshown). The forward end of the oven conveyor will be similarlysupported. The conveyor is of open, gas pervious construction andsuitably may be made of wire mesh material. Means are provided to heatthe material carried by the conveyor. For this purpose any suitableheating system may be employed. For example,

hot air may be circulated from a furnace (not shown) through a duct ill,the heated air being forced through the mat on the conveyor and out ofthe oven through duct 52.

Inthe operation of the above-described apparatus, the condensed mat,treated as previously mentioned, is fed forwardly, initially at anaccelerated speed, between conveyors 28 and 301 until its forward edgeprotrudes beyond the conveyors. The mat [8, when placed on the feedconveyors, is positioned so that the filaments lie generallytransversely of the conveyors, the feeding operation moving the mat inthe direction indicated by the arrows in Fig. 6. The protruding forwardedge of the mat is grasped, suitably by hand, and drawn or expanded intoan elongated web which is passed over table 34 and roll 38 and underroll 48, and carried onto conveyor 44 where the end of the web istemporarily secured in any suitable manner, for example, by weightingit. Feed conveyors 38 and 28 are then driven to constantly feed the matforwardly, and conveyor 44 is driven at a much higher speed tocontinuously draw or expand the mat as it is supplied by the feedconveyors. Table 34 is positioned so that a portion of the flat platepresses against the under surface of the web. Roll 38 is similarlypositioned so that the web is in contact with its upper peripheralportion and roll 48 is positioned so that the web is in contact with itslower peripheral portion.

As mentioned above, conveyor 44 is driven at a much higher speed thanfeed conveyors 28 and 30, the speed differential being such as tostretch the mat to. say, between 60 and 70 times its original length.During the stretching operation the filaments of the several layersshift or slide from directions substantially transverse of the mat orweb, to positions, say, at a 45 angle or greater to the transversedimension of the web to lie in what is here termed a direction"generally longitudinal of the web. The shifting of the fibers isaccompanied by a narrowing of the web as illustrated in Fig. 7. Roll 38is positively driven in the direction indicated by the arrow at a speedpreferably slightly greater than the speed of the oven conveyor, androll 48 is driven at a speed greater than the speed of the oven conveyorand of roll 38. For example, if the oven conveyor is traveling at aspeed of, say, 6' per minute, the surfaces of rolls 38 and 48 may rotateat a speed of, say. 6.3 and 6.6 per minute, respectively. The continuedpull on the web, together with the acand close together.

tion of fast driven roll 40, tensions the web to such an extent that, asit reaches the relatively slower moving oven conveyor, the upper andadjacent layers separate, although tied together by numerousintercrossing or interlocking filaments,-

and form into a series of longitudinally extending, substantiallyparallel corrugations which move into close, laterally adjacentrelationship. Due to the drag of plate 34 and the slower speed of roll38, the lower surface of the web is not tensioned to the same extent, orthe tension is temporarily relieved and, although some eorrugating andseparation of the layers may take place, depending upon the particularoperating conditions, the layers adjacent this surface will berelatively smooth The intermediate layer of the web will vary betweenthe condition of the upper layers and the condition of the lower layersto form a portion of intermediate density and openness of structure. Asthe expanded or pulled web is carried through oven 42, the temperatureis maintained in the oven by the circulation of heated air or otherwise,to the degree required to set and harden the binder to bond thefilaments together into a unitary product.

The extent to which the original mat must be expanded or stretched toproduce the desired effeet will vary, depending upon the weight,filament diameter and character of the original mat.

Where a mat as disclosed in Fig. 2 is desired, the operations areidentical except that the oven (see particularly Fig. 8) is providedwith a pressure conveyor 54 overlying the upper reach of conveyor 44.Pressure conveyor 54 is made adjustable relatively to conveyor 44 by anysuitable means (not shown) and is driven at the same speed as thelatter. Conveyor 54 is similarly of open, wire mesh construction topermit the passage of the heated air therethrough. As the puffed matpasses between the two conveyors it is compressed to the desiredthickness and density and-is maintained in its compressed state duringthe binder setting operation, whereby it will retain its compressedcondition after leaving the oven.

The products made by the instant invention are very resilient andcompressible and, due to the gradation of structure from one surface tothe other, perform admirably as filtering media. The process isrelatively simple and does not require involved equipment.

Having thus described my invention in rather full detail, it will beunderstood that these details need not be strictly adhered to and thatvarious changes and modifications may suggest themselves to one skilledin the art, all falling within the scope of the invention as defined bythe sub- Joined claims.

What I claim is:

I 1. A product comprising a multilayer body of intercrossed filaments,the layers adjacent one face having a continuous succession of adjacentsubstantially parallel undulations extendingat angles to the length ofthe filaments, and forming an openwork structure, and succeeding layershaving similar undulations of diminished depth.

2. A product comprising a unitary multilayer body of intercrossedfilaments, the layers adjacent one face having a continuous successionof adjacent substantially parallel undulations extending at angles tothe length of the filaments, and forming an openwork structure, andsucceeding layers having similar undulations of diminished depth, and aset binder bonding the filaments into the unitary body.

3. A product comprising a multilayer body of intercrossed, glassfilaments, said body being expended in the direction of its thickness toprovide a relatively lightweight, open, porous structure and to providethe layers adjacent one face with a continuous succession of adjacentsubstantially parallel undulations extending at angles to the lengths ofthe filaments and to provide succeeding layers with similar undulationsof diminished depth,

4. A product comprising a multilayer body of intercrossed, glassfilaments, said body being expanded in the direction of its thicknessand the layers adjacent one face thereof having a continuous successionof adjacent substantially parallel, continuous undulations extending atangles to the lengths of the filaments whereby a relatively lightweight,open, porous structure is provided, and succeeding layers having similarundulations of diminished depth whereby said body i of greater densityadjacent the face opposite to said one face.

5. A product comprising a, multilayer, unitary body of intercrossed,glass filaments, said body being expanded in the direction of itsthickness and said layers having a continuous succession of adjacentsubstantially parallel, continuous undulations extending at angles tothe lengths of the filaments, said undulations being of less depthadjacent one surface of the body than the other, and said body being ofgreater density adjacent said one surface.

6. A product comprising a multilayer, unitary body of intercrossed,glass filaments, said body being expanded in the direction of itsthickness and said layers having a continuous succession of adjacentsubstantially parallel, continuous undulations extending at angles tothe lengths of the filaments, said undulations being of less depthadjacent one surface of the body than the other, said body being ofgreater density adjacent said one surface, and a hardened binder bondingthe filaments into the unitary body.

7. A product comprising a compressed, unitary, multilayer body ofintercrossed, glass filaments, said body being expanded in the directionof its thickness and said layers having a continuous succession ofadjacent substantially parallel, continuous undulations extending atangles to the lengths of the filaments, said undulations being of lessdepth adjacent one surface of the body than the other, said body beingof greater density adjacent said one surface, and a hardened binderbonding the filaments into the unitary body.

8. The method comprising drawing a multilayer mat, in which thefilaments of adjacent layers cross each other at acute angles, in adirection at right angles to the general lay of the filaments untillayers of the mat assume an undulatory form and the mat expands in thedirection of its thickness, and retarding the drawing movement of thelayers adjacent one face of the mat to cause the mat to have a greaterdensity adjacent said one face than the other.

9. The method comprising drawin a multilayer mat, in which the filamentsof adjacent layers cross each other at acute angles, in a direction atright angles to the general lay of the filaments until layers of the matassume an undulatory form and the mat expands in the direction of itsthickness, and retarding the movement of the layers adjacent one face ofthe mat to cause relatively minor undulation of the layers adjacent saidone face of said mat and relatively major undulation adjacent theopposite face.

10. The method comprising drawing a multilayer mat, in which thefilaments of adjacent layers cross each other at acute angles and whichcontains an unset binder, in a direction at right angles to the generallay of the filaments until layers of the mat assume an undulatory formand the mat expands in the direction of its thickness, retarding thedrawing movement of the layers adjacent one face of the mat whileaccelerating the drawing movement of the layers adjacent the other faceto cause relatively minor undulation of the layers adjacent said oneface oi the mat and relatively major undulation adjacent the oppositeface, and setting the binder.

11. The method comprising drawing a multilayer glass mat in which thefilaments of adjacent layers cross each other at acute angles in adirection at right angles to the general lay of the filaments untillayers of the mat assume an undulatory form and the mat expands in thedirection of its thickness and during said drawing and expandingoperation contacting one face of the mat with a relatively slower movingsurface and the other face thereof with a relatively rapidly movingsurface to cause greater expansion of said mat adjacent one face thanthe other.

12. The method comprising drawing a multilayer glass mat in which thefilaments of adjacent layers cross each other at acute angles in adirection at right angles to the general lay of the filaments untillayers of the mat assume an undulatory form and the mat expands in thedirection of its thickness and during said drawing and expandingoperation contacting one face of the mat with a relatively slower movingsurface and subsequently contacting the other face of the mat with arelatively rapidly moving surface and then conveying the expanded mataway from the expanding operation.

13. The method comprising feeding a multilayer mat in which thefilaments of adjacent layers cross each other at acute angles, drawingthe mat in a direction at right angles to the general lay of thefilaments until layers of the mat assume an undulatory form and the matexpands in the direction of its thickness, by contacting the mat at apoint remote from the feed by means moving at a, relatively high speed,contacting one face of the mat intermediate said feed and means witharelatively slow moving surface and contacting the other face of the matintermediate said feed and means with a relatively rapidly movingsurface to cause greater expansion of said mat adjacent one face thanthe other.

14. The method comprising drawing a multilayer glass mat containing anunset binder, and in which the filaments of adjacent layers cross eachother at acute angles, until layers of the mat assume an undulatory formand the mat expands in the direction of its thickness, and during saiddrawing and expanding operation contacting one face of the mat with arelatively slower moving surface and the other face thereof with arelatively rapidly moving surface to cause greater expansior of said matadjacent one face than the other, and setting the binder.

15. The method comprising drawing a multilayer glass mat containing anunset binder, and in which the filaments of adjacent layers cross eachother at acute angles, until layers of the mat assume an undulatory formand the mat expands in the direction of its thickness and during saiddrawing and expanding operation contacting one face of the mat with arelatively greater expansion of said mat adjacent one face than theother, compressing the mat and setting the binder.

16. The method comprising feeding a multilayer mat in which thefilaments of adjacent layers cross each other at acute angles, expandingthe mat in a direction at right angles to the general lay of thefilaments until layers of the mat assume an undulatory form and the matexpands in the direction of its thickness and during said expandingoperation drawing one face of the mat over a stationary plate,contacting said face of the mat with a relatively slowly moving surface,and contacting the other face of the mat with a relatively rapidlymoving surface, to cause greater expansion of said mat adjacent one facethan the other.

HARRY E. HOLCOMB.

10 REFERENCES CITED Themfoilowing references are of record in the fileof this patent:

